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The Korean Journal of Pathology 2003;37(1): 58-61.
Type 2 Fiber Predominance in Patients with Muscle Cramp and Exertional Myalgia: A Report of Three Cases.
Na Rae Kim, Sung Hye Park, Lim Suh Yeon, Byung Joon Kim
1Department of Pathology, Kangnam General Hospital Public Corporation, Seoul, Korea
2Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. ylsuh@smc.samsung.co.kr
3Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
4Department of Pathology, Ilsan Paik Hospital, Inje University School of Medicine, Koyang, Korea
Type 2 fiber predominance or a decrease of the type 1/type 2 ratio was rarely reported as the only abnormal pathologic finding in patients suffering from muscle cramp and myalgia. Here, we describe the clinicopathologic findings of three cases of type 2 fiber predominance, presented with muscle cramp and myalgia in otherwise healthy patients. All of them were young men (18, 19 and 22 years). Light microscopic and neurologic examinations, and laboratory data showed mere nonspecific findings that were not concordant with their subjective symptoms. However, enzyme histochemistry performed on muscle biopsy revealed an increased fraction of type 2 fibers; 73%, 80%, and 75%, in each case. The pathogenesis of this entity remains unclear, but the recognition of this unusual clinicopathologic entity is important for both pathologists and neurologists so they can avoid misdiagnoses or unnecessarily tiresome studies. We emphasize that type 2 fiber predominance should be included in the underlying causes of unexplained muscle cramps and exertional myalgia, especially among young adults, although it remains unclear whether the fiber type predominance is a separate entity or a part of other underlying neurologic or systemic disorders.
Key Words: Muscle Cramp; Exertion; Muscle Fibers; Predominance; Myalgia
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